This invention relates generally to vibration control, and more specifically to a system of passive vibration control having adaptive elements.
There are many instances where undesired mechanical vibrations are transmitted through a structure or assembly of structures which are in mechanical communication. Dishwashers, refrigerators, satellite-antennae, heavy machinery, sensitive computer and other electronic equipment, electric generators in an RV or on a ship, stacks and mufflers, and engine-body structure of a vehicle are all examples of structures with vibrating bodies in communication with other structures.
Prior devices have attempted to reduce the amount of vibration in a system by designing passive mounting systems that are mechanically "tuned" to the vibrating body to ensure that system resonances do not occur at primary system operational frequencies, thereby reducing the amount of transmitted noise and vibrations. However, due to wear and tear of the mounting system over time, as well as changes in the dynamic characteristics of the vibrating body and the attached structure, the system may become "out of tune" and vibrations may surpass a desired threshold. Thus a purely passive mounting system, may not satisfy today's specifications.
Further, current industry trends, e.g., appliances and HVAC equipment, have focused on the development of variable speed industrial machinery applications in order to increase operational efficiency and prolong machinery life. As a result, it is no longer practical to seek to use passive elements "tuned" to fixed frequencies to reduce vibrations and noise over the entire operational frequency range.
Various publications and patents have introduced possible solutions in an attempt to solve the above described problems using active vibration control techniques. Others have proposed different techniques for either a modified controller or actuation mechanism or both to compensate for the present problem. However, many of the proposed techniques are designed to work with active noise control and may not be applicable to the vibration control problem. Active vibration control techniques are typically complex, expensive, and may not be economically feasible for many types of industrial machinery. Additionally, active control systems may, in fact, be beyond what is necessary to control vibrations in appliances, generator sets, compressors, etc.
There is a need for a vibration control system which overcomes the shortcomings of a purely passive system, while avoiding the complexity and expense of an active system, and, which is adaptive, on-line, to compensate for variations in system characteristics.